Various systems which assist the driver of a vehicle in keeping the vehicle in, for example, its lane, are known from the prior art. These systems are also referred to as LKS (Lane Keeping Support) systems. Known LKS systems comprise a lane detection system such as, for example, a video system with which the curvature of the lane and the relative position of the vehicle in the lane, the so-called attitude and orientation, can be determined. If the steering angle which is selected by the driver deviates too much from the setpoint steering angle which is predefined by the lane profile, artificial steering forces are applied to the steering of the vehicle using a steering actuator such as, for example, a servomotor. The steering forces are so strong that they can be detected haptically by the driver and indicate to the driver how he should activate the steering system in order to keep the vehicle in its lane.
The lane detection system can be implemented, for example, as a video system whose video signals are processed by signal processing software which supplies the desired geometric data (attitude, orientation, curvature of the lane). Other lane detection systems comprise for example a magnet sensor which determines the position of the vehicle in conjunction with magnets integrated in the roadway, or optionally also radar sensors. A reference steering angle, which would have to be set at the steering system in order to keep the vehicle in its lane in an optimum way, is then calculated from the geometric attitude data and information about the curvature of the lane by means of a mathematical reference model (algorithm). Given a deviation of the driver steering angle from the reference steering angle, an assistance torque is then applied to the steering system using a steering actuator. The assistance torque is calculated here on the basis of a predefined characteristic curve.
Distance sensors are known which indicate to the driver an object which is located in front of or behind the vehicle. Such sensors could also be used laterally on the vehicle. However, such sensors respond continuously if objects, in particular curbstones, are located to the side of the vehicle, even though there is no risk of running over said curbstones if the vehicle travels straight ahead. If a display or warning were to be output to the driver when there are such obstacles, the driver would lose his concentration and pose an additional risk to the traffic.
DE 101 25 966 A1, which is incorporated herein by reference, discloses a bend warning system for motor vehicles, in particular for long motor vehicles. A sensor device detects the steering angle of the front axle of the motor vehicle and, in the case of a plurality of steering axles, also their steering angles. A detection device detects obstacles in the lateral surroundings of the motor vehicle. If the detection device detects an obstacle, a calculation device calculates in advance, on the basis of the steering angle and of the velocity of the vehicle, whether a collision with the obstacle is imminent, and in the event of a risk of collision it generates a warning signal for the driver.
DE 30 28 077 C2, which is incorporated herein by reference, discloses a method for warning the driver of a vehicle about a vehicle traveling on the current lane of said first vehicle. In this context, by means of a radar device the traffic surroundings in front of the vehicle are monitored for the presence of a vehicle traveling in front, and the distance between the driver's own vehicle and a detected vehicle traveling in front, as well as the relative speed thereof, are determined. As a function of these parameters and the velocity of the driver's own vehicle and, if appropriate, further parameters such as the roadway and braking state, a safety distance between the two vehicles is calculated and is then compared with the measured distance. If the measured distance is shorter than the safety distance, a warning signal is generated, and the risk of a collision is displayed on a visual display field. In one variant of the known method, the sensing of surroundings is also extended to the respective area behind on adjacent lanes, so that the anticipated risk of an accident can also be determined in advance of a planned change of lane.
Document DE 195 07 957 C1, which is incorporated herein by reference, discloses a vehicle which is equipped with a system for warning against falling asleep. The vehicle has a laterally mounted optical scanning device for contactless detection of lane markings which laterally bound the vehicle's lane. The sensor data which are made available by the scanning device are fed to an evaluation unit for determining a distance between the vehicle and the detected lane markings. In addition, the evaluation unit determines the lateral speed of the vehicle in relation to the detected lane markings, wherein a warning against falling asleep in the form of an acoustic signal is triggered if it becomes apparent on the basis of the distance present and the lateral speed of the vehicle that exiting from the lane is imminent.
In order to prevent accidents which arise if the driver departs from the actual lane while driving, nowadays systems are used which warn drivers who are deviating from the lane (ASIL—Lane assistant in Citroen). These systems detect the lines on the surface of the road, whether discontinuous or continuous lines, and their colors and widths.
It is necessary in this context for the roads to be provided with lines such as is also prescribed by legislators since otherwise such lane assistants cannot be used. If the vehicle crosses such a line, for example without the activation of a flashing indicator signal, a warning signal is output by vibration of the seat. In this context, driver assistance systems are known such as, for example, an overtaking assistant, as well as the automatic takeover of a speed limiting means.
If a driver assistance system such as Adaptive Cruise Contron (ACC) is activated, the driver can increase the current speed by activating the accelerator pedal, without switching off the ACC function. However, the brake pedal causes the ACC to be switched off, in the same way as manual switching off. At present there is no possible way for the driver to be in command of the vehicle in free situations and allow himself to be led automatically by the ACC as soon as the driving possibilities are limited (and therefore also less fun).